Electronic payment systems and methods involving a mobile device are described, including a device-implemented method for issuing a payment, which includes requesting an authentication code; receiving the authentication code; sending a message to a device of a payee, the message comprising a payment amount and the authentication code; and receiving an acknowledgement of the payment amount. Each of the bottleneck delta VWIP values represents the time until one of n bottleneck workstations begins to risk starvation. The side of the semiconductor chip includes plural conductor pads. A pressure member presses the belt against the heating member. In addition, the fluted sheet can include at least one ridge extending along at least 50% of the flute length between an internal peak and an adjacent external peak.